Manufacture of incandescent lamps.



4 UNITED STATES, PATEn-T OFFICE.

rannnarc w. GILL, or ARLINGTON, NEW annsnr, Assrcnon r ennnnnnnnncrnrc t JOMPANY, A CORPORATION, OF NEW YORK.

MANUFACTURE OF INCANDESCENT LAMPS.

No Drawing.

To all wZwm-it may concern:

Be 1t known that I, Fnnnnnrc W. GILL, a

citizen of the United States, residing at Arlington, county of Hudson, State of New Jersey, have invented certain new and useful Improvements in the Manufacture of 'Incandescent Lamps, of which the following is a specification.

It has been found advantageous to introduce into metallic filament incandescent lamps various solid substances which evolve to the metal of the filament, particularly the metal as given off by the incandescent filament. This atmosphere reacts with the metal of the filament to render the deposit on the filament supports.

on the bulb much more translucent and less light obscuring than would be the case if the getter were not present. These substances, referred to as getters cause a tungsten filament to be attacked if in contact with it, and consequently various expedients have been adopted to keep the substance out of contact with the filament but in such relation to it that the heat radiated from the filament raises the substanceto the proper temperature during the operation of the.

lamp. For example, the substance has been placed in the glass tube to which the fila-. ment supports are secured, has been painted on the central glass stem, or has been placed To apply these substances in any ofthe ways mentioned is a tedious and expensive operation, requiring skilled labor.

The object of my invention is to improve incandescent lamps by introducing the desired substance into the lamp in a novel and most advantageous manner. Another ob ect is to introduce the substance in such an effective manner that a very small quantity suffices, the lamp is not discolored in any way, and the substance is invisible in the finished lamp. A further object is to simplify,

Specification of Letters Patent. Patented N 0V. 12, 1918. Application fll'ed June 29, 1915. Serial No. 37,014.

cheapen and improve'in general the manufacture of incandescent lamps having .in them substances of the character above described. To this end, I apply the substance, preferably in very finely divided.

form, directly to the finished filament at some part which may be rendered highly incandescent by passage of current through the filament. ""1

'I have discovered that although a tung sten filament lamp is of comparatively shortlife and the filament willbe very appreciably attacked if the filament 1s contact with the mass of chemically ac tive solid substance necessary to be used when the substance is placed in lamps in the usual manner, the same substance, when properly applied to apart of the tungsten filament, which becomes highly incandescent when currentis passed. through the lamp, will not cause filament attack to any appreciable extent, but will exert as marked an efiect upon the life and efiiciency of. the lamp as though laced in the lamp in'the usual manner. he best results are obtained when the substance is applied to the filament in a very finely divided state and in the form of a thin, well distributed layer. in intimate contact with the filament: A quantity too small to produce any irridescence or discoloration of the bulb is ample to obtain the efi'ects of the substance on the life and efliciency of the lamp, and if evenly distributed over a filament of the length required for commercial voltages, such as 110 volts, a thinlayer such as can be put on conveniently-will contain about the minimum amount of getter necessary to be used, and, owing to its distribution, will produce a maximum efl'ect. An uneven distribution of the getter is to be avoided as masses or beads of the getter on the filament will cause a marked deterioriation of the filament and will exert such a deleterious effect that the life of the lamp will be less than it would be if no getter were used. This quantity is much less than is necessary when the substance is placed on the stem, the supports, or other parts of the lamp.

The substance may be applied to the filament either before or after the filament has been mounted on its supports. The a lication to the filament may be accomphs ed in various ways, as by painting it on with a brush, spraying it on by means of an atomvehicle. If the substance is applied to the filament before the filament has beenmonntizcr or spraying bottle, or passing the wire through either a solution, or a suspensionof the finel powdered substance in a suitable ed upon its supports, some suitable protective covering for the coated filament maybe desirable to prevent injur 'to the coating during the subsequent hand ing and manipulation of the filament.

After'the substance has been applied to the filament the lamp is exhausted and sealed oil without passing current throu h the filament. After the lamp is sealed, su cient current is passed through the filament to bring it to incandescence whereupon the chemically active substance appears to be driven off the filament and deposited in a finely divided invisible condition. Although the substance cannot be seen' in the lamp after the filament has'been rendered incandescent it nevertheless exerts a marked eifect' in lengthening the life of the lamp and increasing its efficiency.

One desirable way of applying the substance directly tothe filament is to spray it upon the finished filament. Under some 7 conditions, I prefer to finish the mount by placing the filament upon its supports in the usual manner and then spraying the finished mount by means of some suitable,

form of atomizer or spraying bottle, such as is used for spraying, or for painting by.

compressed air. A large number of the mounts can be spaced apart and held in a tray, and all of them sprayed very quickly and easily. It is often advantageous to have the finished mounts hot while the substance is being applied to them, as it adheres better when the mount is hot. By this method some of the substance adheres to the supports and to the glass stem or hub as well as to the filament, but this surplus substance does no harm.

Another way of applying the substance is to apply it to the filament before the filament is placed on the mount, by painting or otherwise treatin the finished filament wire so as to coat it with a thin adherent coating 0on tainingthe substance. The coated filament wire should preferably be provided with some suitable protective covering which will protect the coating and at the same time can be removed when desired without harming the lamp. I prefer to cover the coated wire.

v with a resistant adherent covering which will protect the wire during subsequent ma- This covering 1s ofsuch a uipulations. character that it can easily be removed-when desired without altering the coating, pref- [erably by heating the covering to a temperature too low to aifect the chemically active substance with which the filament is coated.

=The covering I refer t use is an adherent organic materia such -".5is-'- "nitrocellulose or inorganic halogen similar material: For example, I have obtained good results with a solution (3611 posed of two and one-half per cent. of cellulose by weight dissolved in amylacetate. The protective covering may be removed by very slight heating while the'lam is on the pump, or may remain on the filament until the lamp issea-led, as the very. thin-covering of 'collodion or nitrocellulose on the produce any harmcoated filament does not ful effects in the lamp. I

One convenient way of a plying the substance directlyto the finished filament before the filament is mounted upon the supports is to wind the filament wire upon :1

States Patent to Suman, 1,013,572, January,

2, 1912,. and then spray or paint the substance or getter on the wound filament. The

wire should then be coated with the protective covering of nitrocellulose or other material, after which it may be taken off the form as desired and placed upon the supports. .Another-convenient way is to pass the finished filament, before it mounted upon the supports, through a Suspension or. solution of the substance or getter with such a speed of movement and such a concentration of substance as to give the wire a coat ing of the proper amount. For example, the wire may be run in a groove of; a wheel which dips'into a reservoir containing the suspension or -solution of the getter with whlch the wire is to be coated. By the ac- 'tion of the wheel the wire. is wet withthe suspension or solution and may then be dried .in any suitable way, asby assing it through some form of oven or cater, to

leave the getter in the form of a coating on the wire. The coated wire may afterward be passed through the protective covering mixture to provide a protective covering for the coated filament. By

this method a very uniform and evenly distributed coating of the active substance is obtained, and a very thin and uniform protective covering may be obtained.

r The most suitable for use in alamp in accordance with my invention are compounds, such as fiuori'ds or double flu ride of variousmetals,

as for example 'ferricl-fluorid,Fell mange nous fluorid, MnF cryolite and similardouble fluorids, or sodium chlorid and halogen compounds. These materials may be dissolved in a suitable solvent, or a plied suitable form, such as that shown in United lac . to 130 seconds for the material to pass through a 100 cc. pipette, such as the standard used by the Pennsylvania Railroad for oil tests.

Sodium chlorid and similar halogen compounds may be dissolved in water or in a non-aqueous solvent. Under some conditions the sodium chlorid may -crystallize from solution on the filament in comparatively large masses, instead of in a layer composed of fine particles. To secure the proper distribution on the filament, I may use a suspension of finely powdered sodium chlorid in a suitable vehicle. In such cases, I prefer to make the sodium chlorid in the form of almost impalpable powder. One way of doing this is to make a solution of sodium malanate in water and mix with it some (-hlor-acetic-ester. The sodium chlorid is precipitated as an impalpable powder and may then be held in suspension in some non-aqueous vehicle, such as petroleum other, while being sprayed, painted or otherwise deposited upon the filament.

In order to perfect the vacuum in incandescent lamps, it is customary to introduce a small amount of red phosphorus, which is usually driven into the lamp in the form of a vapor. By my invention this operation may be eliminated and the cost of manufacturing correspondingly decreased by mixing a suitable amount of red phosphorus with the substance which is sprayed, painted or otherwise-deposited on the filament. For example, three grams of red phosphorus may be added for each 100 cos.

-of the sodium and iron fluorid suspension above described. When the filament is raised to incandescence, the phosphorus will act to perfect the vacuum, while the chemically active substance will exert its action unhindered by the presence of the phosphorus.

- which consists in coating a light giving portion of the finished filament with a well distributcd layer of inorganic halogen getter insufiieient in amount to produce discoloration of the bulb when the lamp is lighted and so thin at all points that the life of the lamp is increased by the presence of the getter, exhausting and permanently sealing a lamp containing such coated filament, and subsequently raising the filament of the permanently sealed lamp to incandescence to remove the getter from the filament.

,2. The improvement in the manufacture of tungsten filament lamps which consists in coating a light giving portion of the finished pure tungsten filament with a nonaqueous vehicle and a finely powdered inorganic halogen getter disseminated through said vehicle to form on the filament a nonaqueous layer so thin and evenly distributed and so small in amount that there is ,no appreciable deleterious eifect and no discoloration of the bulb, mounting the coated filament in the lamp. exhausting and permanently sealing the lamp hermetically and then bringing the filament in the permanently sealed lamp to incandescenee.

The improvement in the method of manufacturing tungsten filament lamps which consists in spraying on the light giving portions of the finished pure tungsten filament an adherent liquid containing a finely powdered inorganic halogen getter disseminated through it and of such concentration that the getter adhering to the filament is insufiicient in amount or thicksealing the lamp hermetically, and subse-' quently raising the filament of the permanently sealed lamp to incandescence to drive off the getter from the filament.

4. The improvement in the manufacture of tungsten filament lamps which consists in applying torthe light giving portion of the finished. filament a layer of sodium chlorid insufficient in amount and thickness to produce discoloration of the bulb or to cause appreciable attack on the exposed metal in the lamp when the lamp is lighted, assembling and sealing. the lamp with the coated filament therein, and subsequently raising the coated filament to incandescencc in the sealed lamp to drive off the sodium chlorid from the filament.

In witness whereof, I have hereunto set my hand this 26th day of June, 1915.

FREDERIC W. GILL. 

